Cop and a Half (1993)

Devon Butler is an eight-year old who dreams of being a cop. He watches police TV shows, knows police procedures, and plays cops and robbers with his friend Ray. One day, while snooping around in a warehouse, he witnesses a murder. He goes to the police, who want the information, but won't get it until they make Devon a cop. The police then team him with veteran cop (and child hater) Nick McKenna (Burt Reynolds), and the two team up in comic series of events to find the killer.